Electric switch



Patented May 22, 1934 PATENT OFFICE v 1,960,208 ELECTRIC swrrcn Herman J. Hammer-1y, New Britain, Conn., as-

signor to The Trumbull Electric Manufacturing Company, Plainville, Conn., a corporation of Connecticut Application January 13, 1932, Serial No. 586,313

8 Claims.

My invention relates particularly to switches which are operable manually under normal circumstances to open and close apircuit but which are adapted to automatically open the circuit in case of an excessive overload or short circuit in the load line. These devices are sometimes termed circuit breakers.

One object of the present invention is to provide a maximum degree of protection with a minimum simplicity of apparatus.

A special object is to provide a construction which will respond quickly to a short circuit.

A construction of this general character at present in use provides a time lag of something 5 like six minutes on a 50 percent overload and approximately three minutes on a 100 percent overload. Such devices even on a short circuit have considerable time lag. This is a disadvantage because the fuses in the circuit ahead of the circuit breaker are likely to blow before the circuit breaker will operate. It is decidedly advantageous to provide a circuit breaker which will operate more quickly than fuses of approximately the same carrying capacity.

According to my invention I provide a quick break switch mechanism in which the circuit is opened by the armature of a magnet and this armature is held in place by a spring controlled and movable thermostatic latch.

Normally the current flows through the thermostatic device and through the electromagnet coil. The normal tripping action is caused by the bending of the thermostatic device which releases the armature and the movable switch member.

In case of a short circuit which produces a sudden and powerful movement of the armature of the magnet, the switch is released even though the thermostatic device has not yet acted.

Fig. 1 is a perspective view showing parts of a switch embodying my invention.

Fig. 2 is a side view showing the parts of the switch in the open circuit position.

Fig. 3 is a sectional and side view showing the parts of the switch in the closed circuit position.

Fig. 4 is a plan view showing the principal parts of the construction involving my invention, the parts being shown in section.

Fig. 5 shows the relative position of the armature andthermostatic device when the armature has been released by the'action of the thermostatic device.-

Fig. 6 is a similar view showing the parts in the position which they occupywhen the armature has acted to release the switch in spite of a delay in action of the thermostatic device.

Fig. '7 is a perspective view showing the various parts of the construction.

Fig. 8 is a perspective view of a detail.

In the drawings I have shown a commercial form of circuit breaker embodying my invention 0 in which the parts are, for convenience, all mounted on an insulating base 10. The main circuit terminals 11 and 12 are mounted on opposite ends of the base. In the form shown the switch is of the double break type having two sta- 5 tionary contacts 13 and 14, one of which is integrally connected to the terminal 12. The movable switch member 15 is adapted to connect the stationary contacts 13 and 14 in the usual manner.

The protection of the circuit is preferably provided by a bi-metallic thermostatic member 16 and an electromagnet having a coil 17 mounted .on the core 18. For convenience the parts are supported by a metal frame 19 mounted on the 7 base 10.

v The movable switch member 15 is carried by a pivotedarm 20 which is operated manually by a lever or finger piece 21 connected to the arm by links 22 and 23 which are hinged together on the pin 24. A spring 25 on the pin 24 affords a bias between the two links 22 and 23 tending to hold them in the position shown in Fig. 3 or to move them into this relative position when the switch is operated to the on position. A spring 26 coacts with the arm 20 to move it to the open circuit position. The frame is provided with a shoulder 2'7 to serve as an abutment for the finger piece 21 in the closed circuit position of Fig. 3.

It will be understood that the switch is manual ly operated in the usual manner. The parts are held in the closed circuit position by the toggle action of the links 22 and 23. When the finger piece is moved from the closed circuit position of Fig. 3 toward the open circuit position the toggle breaks and the switch opens in the usual manner.

The armature 30 of the electromagnetic system is pivoted to the frame at 31-and provided with an arm 32 which. extends adjacent to one of the toggle links so that, if the switch is in the closed circuit position and the armature is drawn to the magnet core, the toggle action will be tripped and the switch will open with a snap action in the usual manner. A spring 33 interposed between the armature and one end of the 5 core 18 tends to hold the armature away from the magnet core-and the hook 34 limits this outward movement.

.the circuit has back and forth to its and connected in the circuit in series with the magnetcore. This thermostatic strip is supported by an insulating block 35 and a guide tube or channel 36 which slides on pins 37 which for convenience project from one arm of the magnet core 18. This member 36 is slotted at 36' to permit sliding movement in a direction parallel to the length of the thermostatic arm or strip 16 and a spring 38 is provided inside the tube which presses the tube and thermostatic device toward the position shown in Fig. 4.

The insulating member 39 secured to the end of the thermostatic arm 16 is normally interposed in the path of movement of the tip of the armature 30 so that passage of normal current through no tripping efiect on the thermostatic device or on the electromagnetic device. In case of an ordinary overload the thermostatic device will gradually heat up and warp the bimetallic arm 16 so as to remove the tip 39 from the path of movement of the armature. This permits the magnet to attract the armature and trip the switch. v

In case of a short circuit the armature is suddenly attracted to the magnet with suflicient force to overcome the power of the spring 38 and to push the entire thermostatic device to the right, as shown in Fig. 6, thus tripping the switch before any of the fuses in the load circuit would have time to blow. Of course, as soon as the switch opens, the magnet is de-energized and the spring 33 moves the armature back to the normal retracted position. The ends of the armature and thermostatic'arm are so designed and arranged that the armature can be retracted in this manner without interference by the thermostatic arm and the thermostatic arm can warp proper position without interference from the armature. I claim:

l. A circuit breaker comprising the combination in a snap switch construction having an electromagnetic tripping device for the switch including a spring pressed movable armature, of a resiliently mounted thermostatic device having a bi-metallic member coacting with said armature to limit its movement under normal circuit conditions and bodily movable with the armature in response to a short circuit.

2. A circuit breaker comprising the combination in a snap switch construction having an electromagnetic tripping device including a movable armature, of a thermostatic device having a bodily movable bi-metallic element arranged to carry current in series with the magnet coil, said thermostatic device coacting with said armature to limit the movement of the armature under normal circuit conditions and a spring pressed support for said thermostatic device'to permit the action of the armature to overcome the pressure of the spring in response to a short circuit regardless of the latching position of the thermostatic element.

3. In a device of the character described having an electromagnetic system including a movable armature, a resiliently mounted thermostatic device coacting with the armature whereby the thermostatic device is flexed away from the path of movement of the armature upon a predetermined overload and whereby the armature moves the thermostatic device bodily on a short circuit when the thermostat is in the normal armature restraining position.

4. In a snap switch construction of the character described having an electromagnetic system including a movable armature controlling said mechanism, a resiliently mounted bi-metallic thermostatic member interposed in the path of the armature and adapted to be flexed and thus retracted from the path of movement of the armature upon a predetermined overload in the circuit, said armature moving the thermostatic device bodily and releasing the snap action mechanism on a short circuit.

5. In a snap switch of the character described having a spring pressed armature, a flexing thermostatic'element and a slidable support therefor bodily moved by the armature upon short circuit.

6. In a device of the character described having a spring pressed pivoted releasing armature, a spring pressed and bodily movable thermostatic element actuated by the armature upon short circuit and snap action mechanism controlled by said armature.

7. A thermostatic tripping device for a switch construction of the character described having an armature normally attracted toward the core of an electromagnet, which includes a bodily movable and flexible thermostatic arm which prevents movement of the armature when the current flow through the switch is normal, said thermostatic arm being adapted to flex to release the armature and permit opening the circuit upon overload condition, and means for directing the movement of the thermostatic arm so that upon a short circuit the armature can act to operate the switch and open the circuit before the thermostatic arm flexes.

8. A latch for an underset toggle break switch having an electromagnetic release and a thermostatic control for the release, said latch comprising a slide on which the thermostatic member is mounted, and a spring resisting the movement of the slide under normal circuit conditions but said spring being so related to the power of the magnet that upon a short circuit the armature overcomes the resistance of the spring so as to trip the switch.

HERMAN J. HAMMERLY. 

